Sanofi and GSK COVID-19 vaccine candidate demonstrates strong immune responses across all adult age groups in Phase 2 trial

Adjuvanted recombinant COVID-19 vaccine candidate triggered strong
neutralizing antibody responses in all adult age groups
 High immune response after a single dose in patients with prior infection
shows strong booster potential
 Global Phase 3 study expected to start in the coming weeks
PARIS and LONDON – May 17, 2021 – The Sanofi and GSK adjuvanted recombinant
COVID-19 vaccine candidate achieved strong rates of neutralizing antibody responses, in
line with those measured in people who have recovered from COVID-19, in all adult age
groups in a Phase 2 study with 722 volunteers. A global pivotal Phase 3 study is expected
to start in the coming weeks.
The Phase 2 interim results showed 95% to 100% seroconversion following a second
injection in all age groups (18 to 95 years old) and across all doses, with acceptable
tolerability and with no safety concerns. Overall, the vaccine candidate elicited strong
neutralizing antibody levels that were comparable to those generated by natural infection,
with higher levels observed in younger adults (18 to 59 years old). After a single injection,
high neutralizing antibody levels were generated in participants with evidence of prior
SARS-CoV-2 infection, suggesting strong potential for development as a booster vaccine.
“Our Phase 2 data confirm the potential of this vaccine to play a role in addressing
this ongoing global public health crisis, as we know multiple vaccines will be
needed, especially as variants continue to emerge and the need for effective and
booster vaccines, which can be stored at normal temperatures, increases”, said
Thomas Triomphe, Executive Vice President and Global Head of Sanofi Pasteur.
“With these favorable results, we are set to progress to a global Phase 3 efficacy
study. We look forward to generating additional data and working with our partners
around the world to make our vaccine available as quickly as possible.”
Roger Connor, President of GSK Vaccines added: “These positive data show the
potential of this protein-based adjuvanted vaccine candidate in the broader context
of the pandemic, including the need to address variants and to provide for booster
doses. We believe that this vaccine candidate can make a significant contribution
to the ongoing fight against COVID-19 and will move to Phase 3 as soon as
possible to meet our goal of making it available before the end of the year.”
Based on these positive Phase 2 interim results, the companies plan to initiate a global
Phase 3, randomized, double-blind study with the 10µg dose, in combination with GSK’s
pandemic adjuvant, in the coming weeks. This Phase 3 trial is expected to enroll more
than 35,000 adult participants from a broad range of countries and will assess the efficacy
of two vaccine formulations including the D614 (Wuhan) and B.1.351 (South African)
In parallel, the companies intend to conduct booster studies with various variant
formulations in order to assess the ability of a lower dose of the vaccine to generate a
strong booster response regardless of the initial vaccine platform received.
Pending positive Phase 3 outcomes and regulatory reviews, the vaccine is expected to
be approved in the fourth quarter of 2021.
More about the Phase 2 study
The Phase 2 study interim results show that the adjuvanted recombinant vaccine
candidate triggered strong immune response amongst adults of all age groups with 95%
to 100% seroconversion rates and neutralizing antibodies that were comparable to those
generated by natural infection. The high titers observed in the non-naïve population after
one dose of the vaccine candidate also suggest it may have strong potential for use as a
booster vaccine. Full results of the Phase 2 study will be published in a peer-reviewed
The randomized, double-blind, multi-center-dose-ranging study was conducted in healthy
adults aged 18 years of age and older, including those with high risk medical conditions,
to evaluate the safety, reactogenicity, and immunogenicity of two injections given 21 days
apart, with 3 antigen dose levels of 5, 10 and 15 µg. Beginning in February 2021, the study
enrolled 722 volunteers in the U.S. and Honduras. It included equivalent numbers of adults
18 to 59 years and those 60 years and above.
This effort is supported by federal funds from the Biomedical Advanced Research and
Development Authority, part of the office of the Assistant Secretary for Preparedness and
Response at the U.S. Department of Health and Human Services in collaboration with the
U.S. Department of Defense Joint Program Executive Office for Chemical, Biological,
Radiological and Nuclear Defense under Contract # W15QKN-16-9-1002.
About the Sanofi / GSK partnership
In the partnership between the two Companies, Sanofi provides its recombinant antigen
and GSK contributes its pandemic adjuvant, both established vaccine platforms that have
proven successful against influenza. The recombinant technology combined with GSK’s
adjuvant is designed to offer the advantages of stability at temperatures used for routine
vaccines, making it easily implementable and easier to distribute at a global scale through
existing infrastructures where vaccines are stored at normal refrigerator temperature. It
also offers the potential to generate high and sustained immune responses, and the
potential to prevent virus transmission.
Shots on goal in the fight against the COVID-19 pandemic
In addition to the adjuvanted recombinant protein-based vaccine in collaboration with
GSK, Sanofi is developing a messenger RNA vaccine in partnership with Translate Bio.
In March 2021, Sanofi and Translate Bio initiated a Phase 1/2 clinical trial of their mRNA
COVID-19 vaccine candidate, in order to assess safety, immune response and
reactogenicity, after preclinical data showed high neutralizing antibody levels. First results
are expected in the third quarter of 2021.
Sanofi is also committed to providing manufacturing support to other vaccine producers.
The company recently announced it will manufacture up to 200 million doses of Moderna’s
COVID-19 vaccine for the U.S., starting in September 2021. Earlier this year, Sanofi also
announced the company will provide support to BioNTech for 125 million doses for the
European Union. In February, Sanofi said it would support Johnson & Johnson for the
production of its COVID-19 vaccine at a rate of approximately 12 million doses per month.
In addition to developing its two COVID-19 vaccines, Sanofi is the only company to
leverage its manufacturing capacity and expertise for three different COVID-19 vaccines
to support the global vaccines supply and help combat the pandemic.
Find out more about our COVID-19 vaccine candidates.
About GSK
GSK is a science-led global healthcare company with a special purpose: to help people do more, feel better,
live longer. GSK is the leading manufacturer of vaccines globally. For further information please
About Sanofi
Sanofi is dedicated to supporting people through their health challenges. We are a global
biopharmaceutical company focused on human health. We prevent illness with vaccines, provide
innovative treatments to fight pain and ease suffering. We stand by the few who suffer from rare
diseases and the millions with long-term chronic conditions.
With more than 100,000 people in 100 countries, Sanofi is transforming scientific innovation into
healthcare solutions around the globe.
Sanofi, Empowering Life

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